1. Field of the Invention
The present invention relates to an improvement in centrifuge tube. More particularly, it relates to a tubular container for centrifugal separation, which is conveniently used for separating a small amount of a phase having an intermediate specific gravity from the other phases of an emulsion. The tubular container of the invention may also be used for separating a small amount of a lighter particle component from a suspension. The tubular container of the invention is particularly suited for the separation of leukocyte from a blood.
2. Prior Art Statement
The centrifugal separation technique has been used to separate a small amount of a component having an intermediate specific gravity from a multi-phase liquid dispersion composed of plural liquid components which are not miscible with each other. The centrifugal separation technique may also be used to separate a small amount of a particle having a lower specific gravity from a suspension containing particles, for example cell or latex particles, having different specific gravities. However, when the amount of the objective component which is to be separated from the other components is very small relative to the amounts of the other components, the thickness of the layer of the objective component laid over the layer of the component having a higher specific gravity is so thin that collection by pipetting of the objective component layer is extremely difficult. For this reason, by the use of a conventional centrifuge tube, it is difficult to separate a small amount of a component having an intermediate specific gravity in pure state.
For instance, in clinical test for the diagnosis of leukemia of human being or animals, it is necessary to separate neutrophil, monocyte or lymphocyte from the peripheral blood and then subjected to test for examining the presence of cancer virus gene or the presence of abnormality in differentiation.
When the whole blood is subjected to centrifugal separation to separate the leukocyte fraction by applying a centrifugal force of, for example, in the order of 300 g ("g" stands for the acceleration of gravity), the leukocyte fraction which has a specific gravity slightly smaller than that of the erythrocyte fraction is separated to form a thin white layer (which is referred to as "buffy coat" in the art) over the erythrocyte fraction. However, since the quantity of buffy coat is small, the leukocyte fraction is apt to be contaminated with erythrocyte when it is picked up by means of a pipette or capillary. This poses a serious problem in the clinical test where a large quantity of leukocyte should be collected from a small quantity of blood. Although it is possible to allow leukocyte to float in the liquid fraction by the use of the Ficoll-Conray solution, the Ficoll-Conray solution is expensive and it should be removed after the completion of separation. Contaminating erythrocyte may be lysed by the use of a hemolysis reagent. However, the remaining hemoglobin must be removed by rinsing. Accordingly, there is a demand for a simplified technique for separating leukocyte without using any artifact in the diagnosis of the cell image and in the experimental cultivation of leukocyte.